Is thermal conductivity additive for multiple layers of different materials?

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Homework Help Overview

The discussion revolves around the concept of thermal conductivity in relation to multiple layers of different materials. Participants are exploring whether the total thermal conductivity can be considered additive or if it behaves differently based on the arrangement of materials.

Discussion Character

  • Conceptual clarification, Assumption checking, Mixed

Approaches and Questions Raised

  • Participants are debating the nature of thermal conductivity in layered materials, with some suggesting additive properties while others propose a model based on electrical components like resistors and capacitors. Questions about the validity of these models and their implications for thermal conductivity are raised.

Discussion Status

The discussion is active, with differing viewpoints being expressed. Some participants are providing insights into modeling approaches, while others are questioning the assumptions behind these models. There is no explicit consensus yet, but the exploration of ideas is ongoing.

Contextual Notes

Participants are navigating the complexities of thermal conductivity and its comparison to electrical properties, indicating potential gaps in understanding or assumptions about the materials involved.

Xeract
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I think the answer is yes, but I just wanted to check.

If you have several sheets of different material, is the total thermal conductivity the sum of the individual thermal conductivities?
 
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I think you're wrong. The conductivity of the laminate is more like the capacitance of capacitors in series. The total conductivity can't be more than the lowest value in the laminate.
 
I was modelling the conductivity on resistors instead of capacitors. Surely the higher the thermal conductivity the higher the "resistance" to heat flow so they should be modeled as resistors?

(I could be completely wrong on this)
 
You're right about the resistors. But conductivity is the inverse of resistance,
so the addition ( for equal thickness layers) looks like,

[tex]\frac{1}{C_{tot}} = \sum \frac{1}{C_i}[/tex]

which reminds me of capacitors. I could also be wrong.
 

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